Passive Solar

The Zion National Park Visitors Center features passive solar design elements The Zion National Park Visitors Center features passive solar design elements

PASSIVE SOLAR is the smartest, cheapest and most efficient way to utilize abundant (and free) solar energy! Passive solar does not involve the use of mechanical and electrical devices; instead, passive solar technologies and techniques take advantage of the sun’s position throughout the year (and the local climate) to heat, cool, and light a building, improving the buildings’ overall comfort and reducing energy bills. Smart building layout maximizes solar heat gain in winter months and minimizes solar heat gain in summer months.  Strategically designed windows, walls and floors collect, store and redistribute solar energy to keep homes cool in the summer and warm in the winter.

USED FOR:
  • Water heating or space heating
  • Cooling
SECTORS:
  • Residential
  • Commercial

The Five Elements of Passive Solar Home Design

The following five elements constitute a complete passive solar home design. Each performs a separate function, but all five must work together for the design to be successful.

Passive Solar 2

(1) Aperture (Collector): Buildings designed for passive solar heating usually have large, south-facing windows. Typically, the aperture(s) should face within 30 degrees of true south and should not be shaded by other buildings or trees from 9 a.m. to 3 p.m. each day during the heating season.

(2) Absorber: Dark surfaces absorb the most heat, so storage elements - such as a masonry wall, floor, or partition – are covered in aborbent material.  Sunlight hits the surface and is absorbed as heat.

(3) Thermal mass: Solid or liquid materials can store heat produced by sunlight to help regulate the temperature. The difference between the absorber and thermal mass, although they often form the same wall or floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface.

(4) Distribution: The method by which solar heat circulates from the collection and storage points to different areas of the house. A strictly passive design will use the three natural heat transfer modes—conduction, convection, and radiation—exclusively. In some applications, however, fans, ducts, and blowers may help with the distribution of heat through the house.

(5) Control: Elements like roof overhangs or trees can be used to shade buildings in the summer.  Electronic sensing devices can control other household elements to maximize heating or cooling throughout the day.  Sensors can trigger differential thermostats that signal a fan to turn on or off automatically or control vents and dampers that allow or restrict heat flow.  Small changes throughout the day, like automatically opening or closing blinds or awnings, can have a significant impact on the heat absorbed during the day.

Examples of Passive Solar Home Design

Incorporating passive solar design into a new home can drastically reduce the need for supplementary heating and cooling, but some passive solar design elements can be easily achieved by taking advantage of passive solar elements in an existing home.

  • Day lighting is a passive solar design principle that uses sunlight to light the interior spaces of a building.  When combined with energy-efficient lighting at night, daylighting can substantially reduce a building's energy consumption.  Natural sunlight has also been shown to contribute to more satisfied and productive occupants.  Keep blinds open during the day to take advantage of natural sunlight and reduce electricity usage.

  • A sunspace is a room built on the south side of a building. As sunlight passes through glass or other glazing, it warms the sunspace much like a greenhouse. In the winter, proper ventilation allows circulates the heat throughout the building. Sunspaces can be closed off in the summer to trap heat and keep the rest of the building cool.

  • A trombe wall is a very thick, south-facing exterior wall that is painted black or constructed of material that absorbs a high amount of heat. A pane of glass or plastic glazing, installed a few inches in front of the wall, helps hold in the heat. The wall heats throughout the day and slowly releases the collected heat at night as the structure cools.

How do I find a passive solar contractor?

Consult the Utah Chapter of the American Institute of Architects to find an architect with experience in passive solar designs.

What incentives are available for passive solar in Utah?

There is a Federal Tax Credit available for builders of new energy efficient homes until December, 2013. Learn more about incentives for energy efficiency in Utah.

More Resources

 

________

Website content provided by Utah Clean Energy, a 501(c)3 non-profit organization working to stop energy waste, create clean energy, and build a smart energy future in Utah and the western United States.